Appliance devices such as dishwashers, clothing washing machines, dryers, ovens, refrigerators and the like often include electrical control circuits. Such control circuits receive input from the user and control the operation of the appliance device based on the received input. In many cases, the overall operation of the appliance is predefined as a general matter and the user input merely modifies the predefined operation in some way.
For example, the operation of a dishwasher typically involves the processes of filling, washing, draining and rinsing. Such operations involve, among other things, the control of water valves, detergent valves and motor relays. The general sequence of such operations is generally predefined. However, user input may be used to alter the sequence, or to define certain parameters of the sequence. For example, the user input may define whether the wash cycle is normal, light, or heavy. Although the general sequence does not necessarily change dependent upon wash cycle selection, the length of certain processes within the sequence does change.
A typical user input interface for a dishwasher includes a rotary knob and a plurality of pushbutton switches. The rotary knob is attached to a cam that controls the sequence of operations within the dishwasher. The cam has a number of followers that trigger the operation of the various dishwasher components. The cam followers are positioned to cause various operations to be executed in a “programmed” sequence. The user selects a particular cycle by rotating the knob to particular position associated with the selected cycle. Upon actuation, the cam begins to rotate automatically started from the user selected position, performing each operation as defined on the cam “program” from the user-selected point forward. The pushbutton switches are used to activate/deactivate various options that are not available through the cam program. For example, pushbutton switches may be used to selectively activate a heated dry cycle, a delayed start, or a high temperature wash.
More recently, electronic controllers, for example, microprocessors and microcontrollers, have replaced the rotary cam control device. The use of electronic controllers provides flexibility and features not typically available in cam control devices. Moreover, as a general matter, replacement of moving parts, such as electromechanical rotating cams, typically increases reliability in products.
However, the use of electronic controllers has added to the complexity of servicing appliances. Small electronic integrated circuits do not lend themselves to the methods of troubleshooting and repair that have historically been used with mechanical and electromechanical devices. Accordingly, malfunctions in an electronically controlled appliance are more difficult to diagnose and resolve than those of the old, mechanical cam controlled devices.
U.S. patent application Ser. No. 10/264,888, assigned to the assignee of the present invention, discloses a diagnostics tool that utilizes an optical transmitter and an optical receiver in a communication probe for bi-directional communication with an appliance controller through an indicator light of the appliance control panel and an optical detector on an external panel of the appliance. The ability to obtain data information from an electronic controller may be used to obtain diagnostic, operational, or test data from the controller regarding the operation of the appliance.
The optical transmitter of the communication probe may be comprised of a standard LED configured to be driven by an electrical data signal so the LED generates light pulses that correspond to the electrical data signal. The optical receiver of the communication probe may be comprised of a standard LED or a phototransistor that is configured to convert a light signal into a data signal. One limitation of using a standard LED or phototransistor is strength of the signal of the LED or phototransistor to impinging light. When the diagnostic tool is located at the end of an assembly line for application verification, communication speed helps reduce the time required to test each appliance. Therefore, a need exists for improving the response time of the optical receiver at the communication probe.